1. Field of the Invention
The invention relates to a control system and a control method for an internal combustion engine that can use a plurality of kinds of fuel including compressed natural gas (CNG).
2. Description of Related Art
In recent years, internal combustion engines that are operated using CNG as fuel have been known. In such an internal combustion engine, there has been proposed an art of determining that the properties of CNG have changed when the correction amount of air-fuel ratio feedback control is larger than a threshold when the internal combustion engine is first operated after being replenished with CNG, and learning the properties of CNG (e.g., see WO 2013/076811).